RESUMEN
We previously reported that 2-arachidonoylglycerol (2-AG) synthesis by diacylglycerol lipase (DAGL) and lysophosphatidate phosphohydrolase (LPAP) and hydrolysis by monoacylglycerol lipase (MAGL) in rod outer segments (ROS) from bovine retina were differently modified by light applied to the retina. Based on these findings, the aim of the present research was to evaluate whether 2-AG metabolism could be modulated by proteins involved in the visual process. To this end, ROS kept in darkness (DROS) or obtained in darkness and then subjected to light (BROS) were treated with GTPγS and GDPßS, or with low and moderate ionic strength buffers for detaching soluble and peripheral proteins, or soluble proteins, respectively. Only DAGL activity was stimulated by the application of light to the ROS. GTPγS-stimulated DAGL activity in DROS reached similar values to that observed in BROS. The studies using different ionic strength show that (1) the highest decrease in DROS DAGL activity was observed when both phosphodiesterase (PDE) and transducin α (Tα) are totally membrane-associated; (2) the decrease in BROS DAGL activity does not depend on PDE association to membrane, and that (3) MAGL activity decreases, both in DROS and BROS, when PDE is not associated to the membrane. Our results indicate that the bioavailability of 2-AG under light conditions is favored by G protein-stimulated increase in DAGL activity and hindered principally by Tα/PDE association with the ROS membrane, which decreases DAGL activity.
Asunto(s)
Ácidos Araquidónicos , Endocannabinoides , Glicéridos , Segmento Externo de la Célula en Bastón , Animales , Endocannabinoides/metabolismo , Ácidos Araquidónicos/metabolismo , Segmento Externo de la Célula en Bastón/metabolismo , Bovinos , Glicéridos/metabolismo , Fototransducción , Transducina/metabolismo , Luz , Lipoproteína Lipasa/metabolismo , Hidrolasas Diéster Fosfóricas/metabolismo , Visión Ocular/fisiología , Visión Ocular/efectos de los fármacosRESUMEN
Alzheimer's disease (AD) is the most prevalent disorder of senile dementia mainly characterized by amyloid-beta peptide (Aß) deposits in the brain. Cannabinoids are relevant to AD as they exert several beneficial effects in many models of this disease. Still, whether the endocannabinoid system is either up- or down-regulated in AD has not yet been fully elucidated. Thus, the aim of the present paper was to analyze endocannabinoid 2-arachidonoylglycerol (2-AG) metabolism in cerebral cortex synaptosomes incubated with Aß oligomers or fibrils. These Aß conformations were obtained by "aging" the 1-40 fragment of the peptide under different agitation and time conditions. A diminished availability of 2-AG resulting from a significant decrease in diacylglycerol lipase (DAGL) activity was observed in the presence of large Aß1-40 oligomers along with synaptosomal membrane damage, as judged by transmission electron microscopy and LDH release. Conversely, a high availability of 2-AG resulting from an increase in DAGL and lysophosphatidic acid phosphohydrolase activities occurred in the presence of Aß1-40 fibrils although synaptosomal membrane disruption was also observed. Interestingly, neither synaptosomal mitochondrial viability assayed by MTT reduction nor membrane lipid peroxidation assayed by TBARS formation measurements were altered by Aß1-40 oligomers or fibrils. These results show a differential effect of Aß1-40 peptide on 2-AG metabolism depending on its conformation.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Ácidos Araquidónicos/metabolismo , Endocannabinoides/metabolismo , Glicéridos/metabolismo , Fragmentos de Péptidos/metabolismo , Sinaptosomas/metabolismo , Péptidos beta-Amiloides/química , Péptidos beta-Amiloides/ultraestructura , Animales , Corteza Cerebral/metabolismo , Corteza Cerebral/ultraestructura , Humanos , Peroxidación de Lípido , Lipoproteína Lipasa/metabolismo , Microscopía Electrónica de Transmisión , Mitocondrias/metabolismo , Mitocondrias/ultraestructura , Fragmentos de Péptidos/química , Fragmentos de Péptidos/ultraestructura , Agregación Patológica de Proteínas/metabolismo , Agregación Patológica de Proteínas/patología , Ratas Wistar , Sinaptosomas/ultraestructuraRESUMEN
The aim of this work was to study how age-related changes could modify several enzymatic activities that regulate lipid mediator levels in nuclei from rat cerebellum and how these changes are modulated by all-trans retinoic acid (RA), docosahexaenoic acid (DHA) and arachidonic acid (AA). The higher phosphatidate phosphohydrolase activity and lower diacylglycerol lipase (DAGL) activity observed in aged animals compared with adults could augment diacylglycerol (DAG) availability in the former. Additionally, monoacylglycerol (MAG) availability could be high due to an increase in lysophosphatidate phosphohydrolase (LPAPase) activity and a decrease in monocylglycerol lipase activity. Interestingly, RA, DHA and AA were observed to modulate these enzymatic activities and this modulation was found to change in aged rats. In adult nuclei, whereas RA led to high DAG and MAG production through inhibition of their hydrolytic enzymes, DHA and AA promoted high MAG production by LPAPase and DAGL stimulation. In contrast, in aged nuclei RA caused high MAG generation whereas DHA and AA diminished it through LPAPase activity modulation. These results demonstrate that aging promotes a different nuclear lipid metabolism as well as a different type of non-genomic regulation by RA, DHA and AA, which could be involved in nuclear signaling events.
Asunto(s)
Envejecimiento , Ácido Araquidónico/química , Núcleo Celular/metabolismo , Ácidos Docosahexaenoicos/química , Metabolismo de los Lípidos , Tretinoina/química , Animales , Diglicéridos/química , Glicerofosfatos/química , Homeostasis , Hidrólisis , Lipasa/metabolismo , Monoglicéridos/química , Ratas , Ratas Wistar , Transducción de SeñalRESUMEN
2-Arachidonoylglycerol (2-AG) is one of the principal endocannabinoids involved in the protection against neurodegenerative processes. Cannabinoids primarily interact with the seven-segment transmembrane cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2), both of which are expressed in the central nervous system (CNS). The level of 2-AG is controlled through key enzymes responsible for its synthesis or degradation. We have previously observed a deregulation of 2-AG metabolism in physiological aging. The aim of this study was to analyze how 2-AG metabolism is modulated by CB1/CB2 receptors during aging. To this end, both CB1 and CB2 receptor expression and the enzymatic activities (diacylglycerol lipase (DAGL), lysophosphatidate phosphohydrolase (LPAase) and monoacylglycerol lipase (MAGL)) involved in 2-AG metabolism were analyzed in the presence of cannabinoid receptor (CBR) agonists (WIN and JWH) and/or antagonists (SR1 and SR2) in synaptosomes from adult and aged rat cerebral cortex (CC). Our results demonstrate that: (a) aging decreases the expression of both CBRs; (b) LPAase inhibition, due to the individual action of SR1 or SR2, is reverted in the presence of both antagonists together; (c) LPAase activity is regulated mainly by the CB1 receptor in adult and in aged synaptosomes while the CB2 receptor acquires importance when CB1 is blocked; (d) modulation via CBRs of DAGL and MAGL by both antagonists occurs only in aged synaptosomes, stimulating DAGL and inhibiting MAGL activities; (e) only DAGL stimulation is reverted by WIN. Taken together, the results of the present study show that CB1 and/or CB2 receptor antagonists trigger a significant modulation of 2-AG metabolism, underlining their relevance as therapeutic strategy for controlling endocannabinoid levels in physiological aging.
Asunto(s)
Envejecimiento/metabolismo , Ácidos Araquidónicos/metabolismo , Endocannabinoides/metabolismo , Glicéridos/metabolismo , Receptores de Cannabinoides/fisiología , Animales , Membrana Celular/metabolismo , Corteza Cerebral/metabolismo , Lipoproteína Lipasa/metabolismo , Monoacilglicerol Lipasas/metabolismo , Fosfatidato Fosfatasa/metabolismo , Ratas , Ratas Wistar , Receptor Cannabinoide CB1/agonistas , Receptor Cannabinoide CB1/antagonistas & inhibidores , Receptor Cannabinoide CB1/metabolismo , Receptor Cannabinoide CB2/agonistas , Receptor Cannabinoide CB2/antagonistas & inhibidores , Receptor Cannabinoide CB2/metabolismo , Receptores de Cannabinoides/metabolismo , Sinaptosomas/metabolismoRESUMEN
One of the principal monoacylglycerol (MAG) species in animal tissues is 2-arachidonoylglycerol (2-AG), and the diacylglycerol lipase (DAGL) pathway is the most important 2-AG biosynthetic pathway proposed to date. Lysophosphatidate phosphatase (LPAase) activity is part of another 2-AG-forming pathway in which monoacylglycerol lipase (MAGL) is the major degrading enzyme. The purpose of this study was to analyze the manner in which DAGL, LPAase, and MAGL enzymes are modified in the central nervous system (CNS) during aging. To this end, diacylglycerols (DAGs) and MAGs of different composition were used as substrates of DAGL and MAGL, respectively. All enzymatic activities were evaluated in membrane and soluble fractions as well as in synaptic terminals from the cerebral cortex (CC) of adult and aged rats. Results related to 2-AG metabolism show that aging: (a) decreases DAGL-α expression in the membrane fraction whereas in synaptosomes it increases DAGL-ß and decreases MAGL expression; (b) decreases LPAase activity in both membrane and soluble fractions; (c) decreases DAGL and stimulates LPAase activities in CC synaptic terminals; (d) stimulates membrane-associated MAGL-coupled DAGL activity; and (e) stimulates MAGL activity in CC synaptosomes. Our results also reveal that during aging the net balance between the enzymatic activities involved in 2-AG synthesis and breakdown is low availability of 2-AG in CC membrane fractions and synaptic terminals. Taken together, our results lead us to conclude that these enzymes play crucial roles in the regulation of 2-AG tissue levels during aging.
Asunto(s)
Envejecimiento/fisiología , Ácidos Araquidónicos/metabolismo , Endocannabinoides/metabolismo , Glicéridos/metabolismo , Animales , Corteza Cerebral/enzimología , Corteza Cerebral/metabolismo , Diglicéridos/metabolismo , Ácidos Grasos/metabolismo , Immunoblotting , Lipoproteína Lipasa/metabolismo , Masculino , Monoacilglicerol Lipasas/metabolismo , Monoglicéridos/metabolismo , Ratas , Ratas Wistar , Sinaptosomas/enzimología , Sinaptosomas/metabolismoRESUMEN
BACKGROUND: We describe the first occurrence in the fossil record of an aquatic avian twig-nest with five eggs in situ (Early Miocene Tudela Formation, Ebro Basin, Spain). Extensive outcrops of this formation reveal autochthonous avian osteological and oological fossils that represent a single taxon identified as a basal phoenicopterid. Although the eggshell structure is definitively phoenicopterid, the characteristics of both the nest and the eggs are similar to those of modern grebes. These observations allow us to address the origin of the disparities between the sister taxa Podicipedidae and Phoenicopteridae crown clades, and traces the evolution of the nesting and reproductive environments for phoenicopteriforms. METHODOLOGY/PRINCIPAL FINDINGS: Multi-disciplinary analyses performed on fossilized vegetation and eggshells from the eggs in the nest and its embedding sediments indicate that this new phoenicopterid thrived under a semi-arid climate in an oligohaline (seasonally mesohaline) shallow endorheic lacustine environment. High-end microcharacterizations including SEM, TEM, and EBSD techniques were pivotal to identifying these phoenicopterid eggshells. Anatomical comparisons of the fossil bones with those of Phoenicopteriformes and Podicipediformes crown clades and extinct palaelodids confirm that this avian fossil assemblage belongs to a new and basal phoenicopterid. CONCLUSIONS/SIGNIFICANCE: Although the Podicipediformes-Phoenicopteriformes sister group relationship is now well supported, flamingos and grebes exhibit feeding, reproductive, and nesting strategies that diverge significantly. Our multi-disciplinary study is the first to reveal that the phoenicopteriform reproductive behaviour, nesting ecology and nest characteristics derived from grebe-like type strategies to reach the extremely specialized conditions observed in modern flamingo crown groups. Furthermore, our study enables us to map ecological and reproductive characters on the Phoenicopteriformes evolutionary lineage. Our results demonstrate that the nesting paleoenvironments of flamingos were closely linked to the unique ecology of this locality, which is a direct result of special climatic (high evaporitic regime) and geological (fault system) conditions.